Method for manufacturing outer joint member for constant velocity universal joint and outer joint member

ABSTRACT

Provided is a method of manufacturing an outer joint member of a constant velocity universal joint, which is constructed by welding a cup member and a shaft member, the method including: forming the cup member and the shaft member of medium carbon steel; preparing; preparing; bringing the joining end surface of the cup member and the joining end surface of the shaft member into abutment against each other; welding the cup member and the shaft member; and performing, after the welding, ultrasonic flaw detection-inspection from any one of a surface side of the cup member and a surface side of the shaft member, which has the another one of the joining end surface of the cup member and the joining end surface of the shaft member.

TECHNICAL FIELD

The present invention relates to a method of manufacturing an outerjoint member of a constant velocity universal joint and an outer jointmember.

BACKGROUND ART

In a constant velocity universal joint, which is used to construct apower transmission system for automobiles and various industrialmachines, two shafts on a driving side and a driven side are coupled toeach other to allow torque transmission therebetween, and rotationaltorque can be transmitted at a constant velocity even when each of thetwo shafts forms an operating angle. The constant velocity universaljoint is roughly classified into a fixed type constant velocityuniversal joint that allows only angular displacement, and a plungingtype constant velocity universal joint that allows both the angulardisplacement and axial displacement. In a drive shaft configured totransmit power from an engine of an automobile to a driving wheel, forexample, the plunging type constant velocity universal joint is used ona differential side (inboard side), and the fixed type constant velocityuniversal joint is used on a driving wheel side (outboard side).

Irrespective of the plunging type and the fixed type, the constantvelocity universal joint includes, as a main component, an outer jointmember including a cup section having track grooves formed in an innerperipheral surface thereof and engageable with torque transmittingelements, and a shaft section that extends from a bottom portion of thecup section in an axial direction. In many cases, the outer joint memberis constructed by integrally forming the cup section and the shaftsection by subjecting a rod-like solid blank (bar material) to plasticworking such as forging and ironing or processing such as cutting work,heat treatment, and grinding.

Incidentally, as the outer joint member, an outer joint member includinga long shaft section (long stem) may sometimes be used. In order toequalize lengths of a right part and a left part of an intermediateshaft, the long stem is used for an outer joint member on the inboardside that corresponds to one side of the drive shaft. The long stem isrotatably supported by a rolling bearing. Although varied depending onvehicle types, the length of the long stem section is approximately from300 mm to 400 mm in general. In the outer joint member, the long shaftsection causes difficulty in integrally forming the cup section and theshaft section with high accuracy. Therefore, there is known an outerjoint member in which the cup section and the shaft section are formedas separate members, and both the members are joined through frictionpress-contact. Such a friction press-contact technology is described in,for example, Patent Document 1.

An overview of the friction press-contact technology for the outer jointmember described in Patent Document 1 is described with reference toFIG. 23 and FIG. 24. An intermediate product 71′ of an outer jointmember 71 includes a cup member 72 and a shaft member 73, which arejoined through the friction press-contact. As illustrated in FIG. 23,burrs 75 are generated in at least one of inner and outer diameters on ajoining portion 74 along with the press-contact. In order to mount arolling bearing (see FIG. 1) to a shaft section of the intermediateproduct 71′ of the outer joint member 71, as illustrated in FIG. 24, itis necessary to remove the burrs 75 on the radially outer side of thejoining portion 74 through processing such as turning. Althoughillustration is omitted, the intermediate product 71′ is processed intoa finished product of the outer joint member 71 through machining of aspline, snap ring grooves, and the like, and through heat treatment,grinding, and the like. Therefore, the outer joint member 71 and theintermediate product 71′ have slight differences in shape, butillustration of the slight differences in shape is omitted in FIG. 24 tosimplify the description, and the outer joint member 71 being thefinished product and the intermediate product 71′ are denoted by thereference symbols at the same parts. The same applies to the descriptionbelow.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP 2012-57696 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The burrs 75 on the joining portion 74 generated due to the frictionpress-contact described above are quenched by friction heat and coolingthat follows the friction heat. Thus, the burrs 75 have a high hardnessand a distorted shape extended in a radial direction and an axialdirection. Therefore, as illustrated in FIG. 24, when removing the burrs75 on the radially outer side through the turning, a tip for turning isliable to be significantly abraded due to the high hardness and crackeddue to the distorted shape. Therefore, it is difficult to increase theturning speed. In addition, the cutting amount per pass of the tip forturning is decreased, and hence the number of passes is increased, whichcauses a problem in that the cycle time is increased to increase themanufacturing cost.

Further, in order to inspect a joining state of the joining portion 74of the outer joint member 71, when ultrasonic flaw detection, whichenables flaw detection at high speed, is to be performed, an ultrasonicwave is scattered due to the burrs 75 remaining on the radially innerside of the joining portion 74, and hence the joining state cannot bechecked. Therefore, there occurs a problem in that total inspectionthrough the ultrasonic flaw detection cannot be performed after thejoining.

In view of the above-mentioned problems, when the components are joinedthrough laser welding or electron beam welding, the surfaces of thejoining portion may be prevented from being increased in thicknessunlike the case of the friction press-contact. However, when the cupmember 72 and the shaft member 73 as illustrated in FIG. 25 are broughtinto abutment against each other to be welded, a gas pressure in ahollow cavity portion 76 is increased due to processing heat during thewelding, and after completion of the welding, the pressure is decreased.Due to the variation in the internal pressure of the hollow cavityportion 76, blowing of a molten material occurs. Thus, a recess isformed on radially outer surfaces of the welded portion, poor welding interms of depth occurs, and air bubbles are generated inside the weldedportion, thereby degrading the welding state. As a result, the strengthof the welded portion is not stable, which adversely affects quality.

In addition, the cup member 72 and the shaft member 73, which are joinedthrough the friction press-contact as illustrated in FIG. 23 and FIG. 24or joined by welding as illustrated in FIG. 25 as described above, arejoined at an intermediate position on the entire shaft section having ashape and dimensions different for each vehicle type. Accordingly, asdescribed later, it was proved that there is also a problem in terms ofcost reduction achieved through enhancement of productivity andstandardization of a product type of the cup member.

In addition, through the laser welding and the electron beam welding, aweld bead can be prevented from being increased in thickness, and hencethe total inspection through the ultrasonic flaw detection can beperformed. However, the inventors of the present invention have focusedon the fact that the outer joint member is a component of the constantvelocity universal joint being a mass-produced product for automobilesand the like, thereby being essential to enhance accuracy andoperability in inspection on the welded portion.

The present invention has been proposed in view of the above-mentionedproblems, and has an object to provide a method of manufacturing anouter joint member and an outer joint member, which are capable ofincreasing strength of a welded portion and quality, enhancing accuracyand operability in inspection, reducing welding cost, achieving costreduction through enhancement of productivity and standardization of aproduct type, and reducing a burden of production management.

Solutions to the Problems

In order to achieve the above-mentioned object, the inventors of thepresent invention have diligently conducted research and verification toarrive at the following findings. Based on the findings from multipleaspects, the inventors of the present invention have conceived a novelmanufacturing concept in consideration of mass-productivity to achievethe present invention.

(1) In terms of production technology, when the cup member and the shaftmember are welded to each other under a state in which the cup memberand the shaft member are placed in a sealed space and the hollow cavityportion as well as the sealed space is evacuated, blowing of a moltenmaterial and generation of air bubbles are suppressed.

(2) Further, in terms of productivity, when welding is performed on thecup member and the shaft member after being subjected to heat treatmentsuch as quenching and tempering in order to enhance productivity, atemperature of a peripheral portion is increased by heat generatedduring the welding, which causes a risk of reduction in hardness of aregion subjected to heat treatment. To address this problem, theinventors of the present invention have focused on a joining methodinvolving steps capable of achieving highest efficiency and greatestcost reduction without affecting the joint function through change inthe order of the welding step. For example, the following steps areadopted. In a case of a cup member and a shaft member having no risk ofthermal effect during the welding, the cup member and the shaft memberin a finished state after being subjected to heat treatment thatinvolves quenching and tempering are welded to each other. In a case ofa cup member and a shaft member having a risk of thermal effect, on theother hand, the cup member and the shaft member are subjected to heattreatment after the welding. As in this example, the inventors of thepresent invention have found a concept of adopting optimum stepsdepending on shapes, specifications, and the like of the cup member andthe shaft member.

(3) Still further, in terms of productivity and standardization of theproduct type, the inventors of the present invention have found thefollowing problem with the cup member 72 illustrated in FIG. 23 to FIG.25. That is, the cup member 72 has a short shaft section formed byforging or the like to have a diameter smaller than that of the bottomportion of the cup section. This short shaft section is prepared basedon the shape and dimensions of the shaft member 73, and is joined to theshaft member 73 at an intermediate position on the entire shaft section.Depending on a vehicle to which the shaft member 73 is assembled, theshaft member 73 is required to have a variety of shaft diameters andouter peripheral shapes in addition to differences in types such as ageneral length stem type and a long stem type. Therefore, when the shortshaft section of the cup member 72 is prepared based on the shape anddimensions of the shaft member 73, and is joined to the shaft member 73at the intermediate position on the entire shaft section, a cup member72 dedicated to one type of the shaft member 73 is required due todifferences both in shaft diameter (joining diameter) and in shape andlength (joining position) of the short shaft section of the cup member72 to be joined to the shaft member 73. Therefore, it was proved thatthere is a problem also in terms of cost reduction achieved throughenhancement of productivity and standardization of a product type of thecup member.

(4) In addition, the inventors of the present invention have found that,in order to practically achieve the novel manufacturing concept for theouter joint member of the constant velocity universal joint being amass-produced product for automobiles and the like, it is necessary toelaborate an ultrasonic flaw detection-inspection method and a shape ofthe welded portion so that accuracy and operability in inspection on thewelded portion can be enhanced.

As a technical measure to achieve the above-mentioned object, accordingto one embodiment of the present invention, there is provided a methodof manufacturing an outer joint member of a constant velocity universaljoint, which is constructed by forming, through use of separate members,a cup section having track grooves formed at an inner periphery of thecup section and engageable with torque transmitting elements, and ashaft section formed at a bottom portion of the cup section, and bywelding a cup member forming the cup section and a shaft member formingthe shaft section, the method comprising: forming the cup member and theshaft member of medium carbon steel; preparing, as the cup member, a cupmember having a cylindrical portion and a bottom portion integrallyformed by forging, and a joining end surface formed on an outer surfaceof the bottom portion in a machining step after the forging; preparing,as the shaft member, a shaft member having a joining end surface to bejoined to the bottom portion of the cup member, which is formed in amachining step; bringing the joining end surface of the cup member andthe joining end surface of the shaft member into abutment against eachother; welding the cup member and the shaft member by radiating a beamfrom an outer side of the cup member to an abutment portion between thecup member and the shaft member in a radial direction of the cup member,the joining end surface of the cup member having an outer diameter setto an equal dimension for each joint size, the welding being performedunder a state in which a protruding surface protruding to a radiallyinner side with respect to an inner diameter of another one of thejoining end surface of the cup member and the joining end surface of theshaft member is formed on a radially inner side of any one of thejoining end surface of the cup member and the joining end surface of theshaft member; and performing, after the welding, ultrasonic flawdetection-inspection from any one of a surface side of the cup memberand a surface side of the shaft member, which has the another one of thejoining end surface of the cup member and the joining end surface of theshaft member.

Further, according to one embodiment of the present invention for anouter joint member, there is provided an outer joint member of aconstant velocity universal joint, comprising: a cup section havingtrack grooves formed at an inner periphery of the cup section andengageable with torque transmitting elements; and a shaft section formedat a bottom portion of the cup section, the other joint member beingconstructed by forming the cup section and the shaft section through useof separate members, and by welding a cup member forming the cup sectionand a shaft member forming the shaft section, the cup member and theshaft member being formed of medium carbon steel, the cup member havinga cylindrical portion and a bottom portion integrally formed by forging,and a joining end surface formed on an outer surface of the bottomportion, the shaft member having a joining end surface formed at an endportion of the shaft member to be joined to the bottom portion of thecup member, the cup member and the shaft member being welded to eachother under a state in which the joining end surface of the cup memberand the joining end surface of the shaft member are held in abutmentagainst each other, the outer joint member comprising a welded portionbetween the cup member and the shaft member, which is formed of a beadformed by a beam radiated in a radial direction of the cup member froman outer side of the cup member, the joining end surface of the cupmember having an outer diameter set to an equal dimension for each jointsize, the outer joint member comprising a protruding surface protrudingto a radially inner side with respect to an inner diameter of anotherone of the joining end surface of the cup member and the joining endsurface of the shaft member, the protruding surface being formed on aradially inner side of any one of the joining end surface of the cupmember and the joining end surface of the shaft member, the cup memberand the shaft member being welded to each other under a state in whichthe protruding surface is formed.

With the above-mentioned configuration, it is possible to achieve themethod of manufacturing an outer joint member and the outer jointmember, which are capable of increasing the strength of the weldedportion and the quality, reducing the welding cost, enhancing theaccuracy and the operability in the inspection on the welded portion,achieving the cost reduction through the enhancement of productivity ofthe cup member and the shaft member and through the standardization of aproduct type of the cup member, and reducing the burden of productionmanagement.

Specifically, it is preferred that the above-mentioned ultrasonic flawdetection-inspection comprise performing the flaw detection under astate in which the cup member and the shaft member after the welding areplaced under water. With this configuration, the accuracy in theinspection can be further enhanced.

When the above-mentioned protruding surface is formed into the sameshape for each joint size, and when the protruding surface is formed onthe joining end surface of the cup member, a degree of processing forthe cup member to be standardized in product type can be increased. As aresult, the enhancement of productivity and the reduction of the burdenof production management can be further promoted. Further, at the timeof ultrasonic flaw-detection inspection on the welded portion, anultrasonic wave from an angle probe is input from a surface side of theshaft member having a small shaft diameter. Thus, the flaw-detectioninspection can be facilitated.

In this case, in Claims and Specification of the present invention,setting the outer diameter of the joining end surface of the cup memberto an equal dimension for each joint size, and forming the protrudingsurface into the same shape for each joint size are not limited topreparing one type of the cup member for one joint size, that is, notlimited to preparing the cup member assigned with a single productnumber. For example, the present invention encompasses preparing cupmembers of a plurality of types (assigned with a plurality of productnumbers, respectively) for one joint size based on differentspecifications of a maximum operating angle, setting the outer diameterof the joining end surface of each of the cup members to an equaldimension, and forming the protruding surface into the same shape. Inaddition, the present invention encompasses, for example, preparing cupmembers of a plurality of types (assigned with a plurality of productnumbers, respectively) for one joint size in order to achieve managementof the cup members in a plurality of forms including intermediatecomponents before heat treatment and finished components after heattreatment in consideration of the joint function, the circumstances atthe manufacturing site, the productivity, and the like, setting theouter diameter of the joining end surface of each of the cup members toan equal dimension, and forming the protruding surface into the sameshape.

Further, in Claims and Specification of the present invention, settingthe outer diameter of the joining end surface of the cup member to anequal dimension for each joint size, and forming the protruding surfaceinto the same shape for each joint size may be applied also to differenttypes of constant velocity universal joints. For example, the presentinvention encompasses setting outer diameters of the joining endsurfaces of a tripod type constant velocity universal joint and adouble-offset constant velocity universal joint to equal dimensions, andforming the protruding surface into the same shape on the inboard side,and encompasses setting outer diameters of the joining end surfaces of aRzeppa type constant velocity universal joint and an undercut-free typeconstant velocity universal joint to equal dimensions, and forming theprotruding surface into the same shape on the outboard side. Further,the present invention also encompasses setting the outer diameters ofthe joining end surfaces of the constant velocity universal joints onthe inboard side and the outboard side to equal dimensions, and formingthe protruding surface into the same shape on the inboard side and theoutboard side.

At least one of the cup member or the shaft member before the weldingmay be prepared as an intermediate component without performing heattreatment. In this case, the heat treatment and finishing such asgrinding and quenched-steel cutting work are performed after thewelding. Thus, this configuration is suited to a cup member and a shaftmember having such shapes and specifications that the hardness of theheat-treated portion may be affected by temperature rise at theperiphery due to heat generated during the welding. The intermediatecomponent is assigned with a product number for management.

Further, at least one of the cup member or the shaft member before thewelding may be prepared as a finished component subjected to heattreatment. With the at least one of the cup member or the shaft memberprepared as the finished component subjected to the heat treatment andthe finishing such as grinding after the heat treatment orquenched-steel cutting work, it is possible to obtain the cup memberprepared as the finished component for common use for each joint size,and the shaft member having a variety of specifications of the shaftsection for each vehicle type. Thus, the cup member and the shaft memberare each assigned with a product number for management. Therefore, thecost is significantly reduced through the standardization of a producttype of the cup member, and the burden of production management issignificantly alleviated. Further, the cup member prepared for commonuse and the shaft member having a variety of specifications of the shaftsection can be manufactured separately until the cup member and theshaft member are formed into the finished components subjected to thefinishing such as forging, turning, heat treatment, grinding, andquenched-steel cutting work. Further, as well as reduction of setups andthe like, the enhancement of productivity is achieved. However, the cupmember and the shaft member as the finished components are not limitedto members subjected to finishing such as the grinding after the heattreatment or the quenched-steel cutting work as described above. The cupmember and the shaft member according to the present invention encompassmembers assuming a state after completion of heat treatment but beforebeing subjected to the finishing.

The above-mentioned welding comprises electron beam welding. Thus, burrsare not generated on the joining portion. Reduction of manufacturingcost through omission of the number of steps of post-processing for thejoining portion can be reliably achieved, and further, total inspectionon the joining portion through ultrasonic flaw detection can be morereliably performed. Further, deep penetration can be obtained byelectron beam welding, thereby being capable of increasing weldingstrength and reducing thermal strain.

It is desired that the cup member and the shaft member be welded to eachother under a state in which the cup member and the shaft member areplaced in a sealed space to keep a pressure equal to or less than anatmospheric pressure. Accordingly, the blowing of a molten material andthe generation of air bubbles are suppressed, thereby enhancing thestrength and quality of the welded portion.

It is desired that a hardness of a welded portion between the cup memberand the shaft member range from 200 Hv to 500 Hv. When the hardness islower than 200 Hv, it is difficult to secure the strength required interms of a product function, which is undesirable. On the other hand,when the hardness exceeds 500 Hv, there may occur cracking due to phasetransformation and degradation of fatigue strength due to changes intoughness, which are undesirable.

Effects of the Invention

According to the method of manufacturing an outer joint member of aconstant velocity universal joint and the outer joint member of thepresent invention, it is possible to achieve the method of manufacturingan outer joint member and the outer joint member, which are capable ofincreasing the strength of the welded portion and the quality, reducingthe welding cost, enhancing the accuracy and the operability in theinspection on the welded portion, achieving the cost reduction throughthe enhancement of productivity of the cup member and the shaft memberand through the standardization of a product type of the cup member, andreducing the burden of production management.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for illustrating the entire structure of a drive shaftto which an outer joint member according to a first embodiment of thepresent invention is applied.

FIG. 2a is an enlarged partial vertical sectional view for illustratingthe outer joint member of FIG. 1.

FIG. 2b is an enlarged view for illustrating a welded portion of FIG. 2a.

FIG. 2c is an enlarged view for illustrating a shape before welding inFIG. 2 b.

FIG. 3 is a diagram for illustrating an overview of manufacturing stepsfor the outer joint member of FIG. 1.

FIG. 4a is a vertical sectional view for illustrating a cup memberbefore welding and after ironing.

FIG. 4b is a vertical sectional view for illustrating the cup memberbefore welding and after turning.

FIG. 5a is a front view for illustrating a shaft member before welding,that is, a bar material being a blank.

FIG. 5b is a partial vertical sectional view for illustrating the shaftmember before welding and after forging.

FIG. 5c is a partial vertical sectional view for illustrating the shaftmember before welding and after turning and spline processing.

FIG. 6 is a view for illustrating an overview of a welding step.

FIG. 7 is a view for illustrating an overview of the welding step.

FIG. 8 is a front view for illustrating an overview of an ultrasonicflaw detection-inspection apparatus.

FIG. 9 is a plan view for illustrating the overview of the ultrasonicflaw detection-inspection apparatus.

FIG. 10 is a front view for illustrating the overview of the ultrasonicflaw detection-inspection apparatus.

FIG. 11 is a plan view for illustrating the overview of the ultrasonicflaw detection-inspection apparatus.

FIG. 12a is a partial enlarged view as viewed from the arrow F-F of FIG.10, for illustrating a case of a non-defective welded product.

FIG. 12b is a partial enlarged view as viewed from the arrow F-F of FIG.10, for illustrating a defective welded product.

FIG. 13 is a view for illustrating findings in the course ofdevelopment.

FIG. 14 is a front view for illustrating a shaft member assigned with adifferent product number.

FIG. 15 is a partial vertical sectional view for illustrating an outerjoint member that is manufactured using the shaft member illustrated inFIG. 14.

FIG. 16 is a diagram for illustrating an example of standardization of aproduct type of the cup member.

FIG. 17a is a partial vertical sectional view for illustrating amodification of the outer joint member according to the firstembodiment.

FIG. 17b is an enlarged view for illustrating a welded portion of FIG.17 a.

FIG. 17c is an enlarged view for illustrating a shape before welding inFIG. 17 b.

FIG. 18 is a vertical sectional view for illustrating the entirety of acup member of FIG. 17 c.

FIG. 19 is a diagram for illustrating an overview of a method ofmanufacturing an outer joint member according to a second embodiment ofthe present invention.

FIG. 20 is a diagram for illustrating an overview of a method ofmanufacturing an outer joint member according to a third embodiment ofthe present invention.

FIG. 21 is a partial vertical sectional view for illustrating a constantvelocity universal joint using an outer joint member according to thesecond embodiment of the present invention.

FIG. 22 is a partial vertical sectional view for illustrating the outerjoint member of FIG. 21.

FIG. 23 is a vertical sectional view for illustrating an outer jointmember according to a related art.

FIG. 24 is a vertical sectional view for illustrating the outer jointmember according to the related art.

FIG. 25 is a vertical sectional view for illustrating an outer jointmember according to a related art.

EMBODIMENTS OF THE INVENTION

Now, description is made of embodiments of the present invention withreference to the drawings.

FIG. 3 to FIG. 16 are views for illustrating a method of manufacturingan outer joint member of a constant velocity universal joint accordingto a first embodiment of the present invention, and FIG. 1 and FIG. 2are views for illustrating an outer joint member according to the firstembodiment of the present invention. First, the outer joint memberaccording to the first embodiment is described with reference to FIG. 1and FIG. 2, and subsequently, the method of manufacturing an outer jointmember according to the first embodiment is described with reference toFIG. 3 to FIG. 16.

FIG. 1 is a view for illustrating the entire structure of a drive shaft1 using an outer joint member 11 according to the first embodiment. Thedrive shaft 1 mainly comprises a plunging type constant velocityuniversal joint 10 arranged on a differential side (right side of FIG.1: hereinafter also referred to as “inboard side”), a fixed typeconstant velocity universal joint 20 arranged on a driving wheel side(left side of FIG. 1: hereinafter also referred to as “outboard side”),and an intermediate shaft 2 configured to couple both the constantvelocity universal joints 10 and 20 to allow torque transmissiontherebetween.

The plunging type constant velocity universal joint 10 illustrated inFIG. 1 is a so-called double-offset type constant velocity universaljoint (DOJ). The constant velocity universal joint 10 comprises theouter joint member 11 comprising a cup section 12 and a long shaftsection (hereinafter referred to also as “long stem section”) 13 thatextends from a bottom portion of the cup section 12 in an axialdirection, an inner joint member 16 housed along an inner periphery ofthe cup section 12 of the outer joint member 11, balls 41 serving astorque transmitting elements that are arranged between track grooves 30and 40 of the outer joint member 11 and the inner joint member 16, and acage 44 having a spherical outer peripheral surface 45 and a sphericalinner peripheral surface 46 that are fitted to a cylindrical innerperipheral surface 42 of the outer joint member 11 and a spherical outerperipheral surface 43 of the inner joint member 16, respectively, andbeing configured to retain the balls 41. A curvature center O₁ of thespherical outer peripheral surface 45 and a curvature center O₂ of thespherical inner peripheral surface 46 of the cage 44 are offsetequidistantly from a joint center O toward opposite sides in the axialdirection.

An inner ring of a support bearing 6 is fixed to an outer peripheralsurface of the long stem section 13, and an outer ring of the supportbearing 6 is fixed to a transmission case with a bracket (not shown).The outer joint member 11 is supported by the support bearing 6 in afreely rotatable manner, and when the support bearing 6 as describedabove is provided, vibration of the outer joint member 11 during drivingor the like is prevented as much as possible.

The fixed type constant velocity universal joint 20 illustrated in FIG.1 is a so-called Rzeppa type constant velocity universal joint, andcomprises an outer joint member 21 comprising a bottomed cylindrical cupsection 21 a and a shaft section 21 b that extends from a bottom portionof the cup section 21 a in the axial direction, an inner joint member 22housed along an inner periphery of the cup section 21 a of the outerjoint member 21, balls 23 serving as torque transmitting elements thatare arranged between the cup section 21 a of the outer joint member 21and the inner joint member 22, and a cage 24, which is arranged betweenan inner peripheral surface of the cup section 21 a of the outer jointmember 21 and an outer peripheral surface of the inner joint member 22,and is configured to retain the balls 23. Note that, as the fixed typeconstant velocity universal joint 20, an undercut-free type constantvelocity universal joint may sometimes be used.

The intermediate shaft 2 comprises splines 3 for torque transmission(including serrations; the same applies hereinafter) at outerperipheries on both end portions thereof. The spline 3 on the inboardside is spline-fitted to a hole portion of the inner joint member 16 ofthe plunging type constant velocity universal joint 10. Thus, theintermediate shaft 2 and the inner joint member 16 of the plunging typeconstant velocity universal joint 10 are coupled to each other to allowtorque transmission therebetween. Further, the spline 3 on the outboardside is spline-fitted to a hole portion of the inner joint member 22 ofthe fixed type constant velocity universal joint 20. Thus, theintermediate shaft 2 and the inner joint member 22 of the fixed typeconstant velocity universal joint 20 are coupled to each other to allowtorque transmission therebetween. Although the solid intermediate shaft2 is illustrated, a hollow intermediate shaft may be used instead.

Grease is sealed inside both the constant velocity universal joints 10and 20 as a lubricant. To prevent leakage of the grease to an outside ofthe joint or entry of a foreign matter from the outside of the joint,bellows boots 4 and 6 are respectively mounted to a portion between theouter joint member 11 of the plunging type constant velocity universaljoint 10 and the intermediate shaft 2 and a portion between the outerjoint member 21 of the fixed type constant velocity universal joint 20and the intermediate shaft 2.

The outer joint member according to the first embodiment is describedwith reference to FIG. 2. FIG. 2 are enlarged views for illustrating theouter joint member 11 according to this embodiment. FIG. 2a is a partialvertical sectional view. FIG. 2b is an enlarged view for illustrating acircle “A” of FIG. 2a . FIG. 2c is a view for illustrating a shapebefore welding. The outer joint member 11 comprises the bottomedcylindrical cup section 12 that is opened at one end and has thecylindrical inner peripheral surface 42 and the plurality of trackgrooves 30, on which the balls 41 (see FIG. 1) are caused to roll,formed equiangularly on the inner peripheral surface, and the long stemsection 13 that extends from the bottom portion of the cup section 12 inthe axial direction and comprises a spline Sp serving as a torquetransmitting coupling portion formed at an outer periphery on an endportion thereof on an opposite side to the cup section 12. In thisembodiment, the outer joint member 11 is formed by welding a cup member12 a and a shaft member 13 a to each other.

The cup member 12 a illustrated in FIG. 2a to FIG. 2c is anintegrally-formed product being made of medium carbon steel, such asS53C, containing carbon of from 0.40 wt % to 0.60 wt %, and having acylindrical portion 12 a 1 and a bottom portion 12 a 2. The cylindricalportion 12 a 1 has the track grooves 30 and the cylindrical innerperipheral surface 42 formed at an inner periphery thereof. A projectingportion 12 a 3 is formed at the bottom portion 12 a 2 of the cup member12 a. A boot mounting groove 32 is formed at an outer periphery of thecup member 12 a on the opening side thereof, whereas a snap ring groove33 is formed at an inner periphery of the cup member 12 a on the openingside thereof. A bearing mounting surface 14 and a snap ring groove 15are formed at an outer periphery of the shaft member 13 a on the cupmember 12 a side, whereas the spline Sp is formed at an end portion ofthe shaft member 13 a on an opposite side.

The shaft member 13 a is made of medium carbon steel, such as S40C,containing carbon of from 0.30 wt % to 0.55 wt %. A joining end surface50 formed at the projecting portion 12 a 3 of the bottom portion 12 a 2of the cup member 12 a and a joining end surface 51 formed at an endportion of the shaft member 13 a on the cup member 12 a side are broughtinto abutment against each other, and are welded to each other byelectron beam welding performed from an outer side of the cup member 12a in a radial direction. As illustrated in FIG. 2a and FIG. 2b , awelded portion 49 is formed of a bead, which is formed by a beamradiated from a radially outer side of the cup member 12 a. Althoughdetailed description is made later, outer diameters B of the joining endsurface 50 and the joining end surface 51 (see FIG. 4b and FIG. 5c ) areset to equal dimensions for each joint size. However, the outer diameterB of the joining end surface 50 of the cup member 12 a and the outerdiameter B of the joining end surface 51 of the shaft member 13 a neednot be set to equal dimensions. In consideration of for example, a stateof the weld bead, a dimensional difference may be given as appropriatein such a manner that the outer diameter B of the joining end surface 51is set slightly smaller than the outer diameter B of the joining endsurface 50 (the dimensional relationship between the outer diameter B ofthe joining end surface 50 and the outer diameter B of the joining endsurface 51 is consistent throughout specification.

The welded portion 49 is formed on the joining end surface 51 located onthe cup member 12 a side with respect to the bearing mounting surface 14of the shaft member 13 a, and hence the bearing mounting surface 14 andthe like can be processed in advance so that post-processing afterwelding can be omitted. Further, due to the electron beam welding, burrsare not generated at the welded portion. Thus, post-processing for thewelded portion can also be omitted, which can reduce manufacturing cost.Still further, total inspection on the welded portion through ultrasonicflaw detection can be performed. Note that, features of this embodimentreside in an ultrasonic flaw detection-inspection method and a shape ofthe welded portion, which are capable of enhancing accuracy andoperability in inspection on the welded portion in order to practicallyachieve the novel manufacturing concept for the outer joint member ofthe constant velocity universal joint being a mass-produced product.Details thereof are described later.

As illustrated in FIG. 2c , an inner diameter D of the joining endsurface 50 of the cup member 12 a is set smaller than an inner diameterE of the joining end surface 51 of the shaft member 13 a. On the joiningend surface 50 of the cup member 12 a, a protruding surface 50 aprotruding to a radially inner side with respect to the inner diameter Eof the joining end surface 51 of the shaft member 13 a is formed. Insuch a state, the cup member 12 a and the shaft member 13 a are weldedto each other. The protruding surface 50 a is formed into the same shapefor each joint size.

Next, the manufacturing method according to the first embodiment of thepresent invention is described with reference to FIG. 3 to FIG. 16.Before description of details of the features of the manufacturingmethod of this embodiment, that is, an ultrasonic flawdetection-inspection step for the welded portion, an overview ofmanufacturing steps (processing steps) is described. FIG. 3 is anillustration of the overview of the manufacturing steps for the outerjoint member. In this embodiment, as illustrated in FIG. 3, the cupmember 12 a is manufactured through manufacturing steps comprising a barmaterial cutting step S1 c, a forging step S2 c, an ironing step S3 c,and a turning step S4 c. On the other hand, the shaft member 13 a ismanufactured through manufacturing steps comprising a bar materialcutting step S1 s, a turning step S2 s, and a spline processing step S3s. Intermediate components of the cup member 12 a and the shaft member13 a thus manufactured are each assigned with a product number formanagement.

After that, the cup member 12 a and the shaft member 13 a are subjectedto a welding step S6, an ultrasonic flaw detection-inspection step S6K,a heat treatment step S7, and a grinding step S8 so that the outer jointmember 11 is completed. A machining step described in Claims refers tothe turning step S4 c and the turning step S2 s among theabove-mentioned manufacturing steps, and to a grinding step S5 sdescribed later (see FIG. 20).

An overview of each step is described. Each step is described as atypical example, and appropriate modification and addition may be madeto each step as needed. First, the manufacturing steps for the cupmember 12 a are described.

[Bar Material Cutting Step S1 c]

A bar material is cut into a predetermined length in accordance with aforging weight, thereby producing a billet.

[Forging Step S2 c]

The billet is subjected to forging so as to integrally form thecylindrical portion, the bottom portion, and the projecting portion as apreform of the cup member 12 a.

[Ironing Step S3 c]

Ironing is performed on the track grooves 30 and the cylindrical innerperipheral surface 42 of the preform, thereby finishing the innerperiphery of the cylindrical portion of the cup member 12 a.

[Turning Step S4 c]

In the preform after ironing, the outer peripheral surface, the bootmounting groove 32, the snap ring groove 33 and the like, and thejoining end surface 50 are formed by turning. In this embodiment, afterthe turning step S4 c, the cup member 12 a in the form of anintermediate component is assigned with a product number for management.

Next, the manufacturing steps for the shaft member 13 a are described.

[Bar Material Cutting Step S1 s]

A bar material is cut into a predetermined length in accordance with thetotal length of the shaft section, thereby producing a billet. Afterthat, the billet may be forged into a rough shape by upset forgingdepending on the shape of the shaft member 13 a.

[Turning Step S2 s]

The outer peripheral surface of the billet (bearing mounting surface 14,snap ring groove 15, minor diameter of the spline, end surface, and thelike) and the joining end surface 51 of the billet at the end portion onthe cup member 12 a side are formed by turning.

[Spline Processing Step S3 s]

The spline is formed by rolling in the shaft member after turning. Notethat, the method of processing the spline is not limited to the rolling,but press working or the like may be adopted instead as appropriate. Inthis embodiment, after the spline processing, the shaft member 13 a inthe form of an intermediate component is assigned with a product numberfor management.

Next, the manufacturing steps in the process of completing the outerjoint member 11 from the cup member 12 a and the shaft member 13 a aredescribed.

[Welding Step S6]

The joining end surface 50 of the cup member 12 a and the joining endsurface 51 of the shaft member 13 a are brought into abutment againstand welded to each other.

[Ultrasonic Flaw Detection-Inspection Step S6 k]

The welded portion 49 between the cup member 12 a and the shaft member13 a is inspected by the ultrasonic flaw-detection method.

[Heat Treatment Step S7]

Induction quenching and tempering are performed as heat treatment on atleast the track grooves 30 and the cylindrical inner peripheral surface42 of the cup section 12 after welding and a necessary range of theouter periphery of the shaft section 13 after welding. Heat treatment isnot performed on the welded portion. A hardened layer having a hardnessof approximately from 58 HRC to 62 HRC is formed on each of the trackgrooves 30 and the cylindrical inner peripheral surface 42 of the cupsection 12. Further, a hardened layer having a hardness of approximatelyfrom 50 HRC to 62 HRC is formed in a predetermined range of the outerperiphery of the shaft section 13.

[Grinding Step S8]

After the heat treatment, the bearing mounting surface 14 of the shaftsection 13 and the like are finished by grinding. Thus, the outer jointmember 11 is completed.

In the manufacturing steps of this embodiment, the heat treatment stepis provided after the welding step, and hence the manufacturing stepsare suited to a cup member and a shaft member having such shapes andspecifications that the hardness of the heat-treated portion may beaffected by temperature rise at the periphery due to heat generatedduring the welding.

Next, main constituent features of the manufacturing method of thisembodiment are described in detail. FIG. 4a is a vertical sectional viewfor illustrating a state after ironing of the cup member 12 a. FIG. 4bis a vertical sectional view for illustrating a state after turning. Ina preform 12 a′ for the cup member 12 a, a cylindrical portion 12 a 1′,a bottom portion 12 a 2′, and a projecting portion 12 a 3′ areintegrally formed in the forging step S2 c. After that, the trackgrooves 30 and the cylindrical inner peripheral surface 42 are formed byironing in the ironing step S3 c so that the inner periphery of thecylindrical portion 12 a 1′ is finished as illustrated in FIG. 4 a.

After that, in the turning step S4 c, the outer peripheral surface, theboot mounting groove 32, the snap ring groove 33, and the like of thecup member 12 a as well as the joining end surface 50 of the projectingportion 12 a 3 of the bottom portion 12 a 2 and the joining end surface50 having the outer diameter B and the inner diameter D are formed byturning as illustrated in FIG. 4 b.

FIG. 5 are illustrations of states of the shaft member 13 a in therespective processing steps. FIG. 5a is a front view for illustrating abillet 13 a″ obtained by cutting a bar material. FIG. 5b is a partialvertical sectional view for illustrating a preform 13 a′ obtained byforging the billet 13 a″ into a rough shape by upset forging. FIG. 5c isa partial vertical sectional view for illustrating the shaft member 13 aafter turning and spline processing.

The billet 13 a″ illustrated in FIG. 5a is produced in the bar materialcutting step S1 s. The preform 13 a′ is produced by increasing, ifnecessary, the shaft diameter of the billet 13 a″ in a predeterminedrange and forming a recessed portion 52 at a joining-side end portion(end portion on the cup member 12 a side) by upset forging asillustrated in FIG. 5 b.

After that, in the turning step S2 s, the outer diameter of the shaftmember 13 a, the bearing mounting surface 14, the snap ring groove 16,an inner diameter portion 53 (inner diameter E) of the recessed portion52, the joining end surface 51, and the joining end surface 50 havingthe outer diameter B are formed by turning as illustrated in FIG. 5c .In the spline processing step S3 s, the spline Sp is processed at theend portion on the opposite side to the recessed portion 52 by rollingor press forming.

The outer diameter B of the joining end surface 50 located at theprojecting portion 12 a 3 of the bottom portion 12 a 2 of the cup member12 a illustrated in FIG. 4b is set to an equal dimension for one jointsize. Further, in the shaft member 13 a illustrated in FIG. 5c , whichis used as a long stem shaft, the outer diameter B of the joining endsurface 51 located at the end portion on the cup member 12 a side is setto an equal dimension to the outer diameter B of the joining end surface50 of the cup member 12 a irrespective of the shaft diameter and theouter peripheral shape. Still further, the joining end surface 51 of theshaft member 13 a is located at the position on the cup member 12 a sidewith respect to the bearing mounting surface 14. Through the setting ofdimensions as described above, the outer joint member 11 compatible withvarious vehicle types can be manufactured in such a manner that, whilethe cup member 12 a is prepared for common use, only the shaft member 13a is manufactured to have a variety of shaft diameters, lengths, andouter peripheral shapes depending on vehicle types, and both the members12 a and 13 a are welded to each other. Details of the preparation ofthe cup member 12 a for common use are described later.

Next, a method of welding the cup member 12 a and the shaft member 13 ais described with reference to FIG. 6 and FIG. 7. FIG. 6 and FIG. 7 areviews for illustrating an overview of a welding apparatus. FIG. 6 is anillustration of a state before welding. FIG. 7 is an illustration of astate during welding. As illustrated in FIG. 6, a welding apparatus 100mainly comprises an electron gun 101, a rotation device 102, a chuck103, a center hole guide 104, a tailstock 105, workpiece supports 106, acenter hole guide 107, a case 108, and a vacuum pump 109.

The cup member 12 a and the shaft member 13 a being workpieces areplaced on the workpiece supports 106 arranged inside the weldingapparatus 100. The chuck 103 and the center hole guide 107 arranged atone end of the welding apparatus 100 are coupled to the rotation device102. The chuck 103 grips the cup member 12 a to rotate the cup member 12a under a state in which the center hole guide 107 has centered the cupmember 12 a. The center hole guide 104 is integrally mounted to thetailstock 105 arranged at the other end of the welding apparatus 100.Both the center hole guide 104 and the tailstock 106 are configured toreciprocate in the axial direction (lateral direction of FIG. 7).

A center hole of the shaft member 13 a is set on the center hole guide104 so that the shaft member 13 a is centered. The vacuum pump 109 isconnected to the case 108 of the welding apparatus 100. A “sealed space”herein refers to a space 111 defined by the case 108. In thisembodiment, the cup member 12 a and the shaft member 13 a are entirelyreceived in the sealed space 111. The electron gun 101 is arranged at aposition corresponding to the joining end surfaces 50 and 51 of the cupmember 12 a and the shaft member 13 a. The electron gun 101 isconfigured to approach the workpieces up to a predetermined position.

Next, the operation of the welding apparatus 100 constructed asdescribed above and the welding method are described. The cup member 12a and the shaft member 13 a being workpieces are stocked at a placedifferent from the place of the welding apparatus 100. The respectiveworkpieces are taken out by, for example, a robot, are conveyed into thecase 108 of the welding apparatus 100 opened to the air as illustratedin FIG. 6, and are set at predetermined positions on the workpiecesupports 106. At this time, the center hole guide 104 and the tailstock105 are retreated to the right side of FIG. 6, and hence a gap is formedbetween the joining end surfaces 50 and 51 of the cup member 12 a andthe shaft member 13 a. After that, a door (not shown) of the case 108 isclosed and the vacuum pump 109 is activated to reduce the pressure inthe sealed space 111 defined in the case 108. Thus, the pressures in aninner diameter portion 50 b of the cup member 12 a and the recessedportion 52 and the inner diameter portion 53 of the shaft member 13 aare reduced as well.

When the pressure in the sealed space 111 is reduced to a predeterminedpressure, the center hole guide 104 and the tailstock 105 are advancedto the left side as illustrated in FIG. 7 to eliminate the gap betweenthe joining end surfaces 50 and 61 of the cup member 12 a and the shaftmember 13 a. Thus, the cup member 12 a is centered by the center holeguide 107 and fixed by the chuck 103, whereas the shaft member 13 a issupported by the center hole guide 104. After that, the workpiecesupports 106 are moved away from the workpieces. At this time, thedistance between the workpiece supports 106 and the workpieces may beinfinitesimal, and hence illustration of this distance is omitted fromFIG. 7. As a matter of course, the welding apparatus 100 may have such astructure that the workpiece supports 106 are retreated downwardgreatly.

Although illustration is omitted, the electron gun 101 is then caused toapproach the workpieces up to a predetermined position and theworkpieces are rotated to start pre-heating. As a pre-heating condition,unlike the welding condition, the temperature is set lower than thewelding temperature by, for example, radiating an electron beam under astate in which the electron gun 101 is caused to approach the workpiecesso as to increase the spot diameter. Through the pre-heating, thecooling rate after welding is reduced, thereby being capable ofpreventing a quenching crack. When a predetermined pre-heating time haselapsed, the electron gun 101 is retreated to a predetermined position,and radiates the electron beam from the outer side of the workpieces inthe radial direction to start welding. When the welding is finished, theelectron gun 101 is retreated and the rotation of the workpieces isstopped.

Although illustration is omitted, the sealed space 111 is then opened tothe air. Then, the center hole guide 104 and the tailstock 105 areretreated to the right side and the chuck 103 is opened under a state inwhich the workpiece supports 106 are raised to support the workpieces.After that, for example, the robot grips the workpieces, takes theworkpieces out of the welding apparatus 100, and places the workpiecesinto alignment on a cooling stocker. In this embodiment, the cup member12 a and the shaft member 13 a are entirely received in the sealed space111, and hence the configuration of the sealed space 111 defined in thecase 108 can be simplified.

Specifically, the cup member 12 a having a carbon content of from 0.4%to 0.6% and the shaft member 13 a having a carbon content of from 0.3%to 0.55% were used and welded to each other in the above-mentionedwelding apparatus 100 under the condition that the pressure in thesealed space 111 defined in the case 108 was set to 6.7 Pa or less. Inorder to prevent the cup member 12 a and the shaft member 13 a frombeing cooled rapidly after the welding to suppress increase in hardnessof the welded portion, the joining end surfaces 50 and 51 of the cupmember 12 a and the shaft member 13 a were soaked by pre-heating to havea temperature of from 300° C. to 650° C., and then electron beam weldingwas performed. As a result, a welded portion having a projecting heightfrom the welded surface (0.5 mm or less), which imposed no adverseeffect on a product function, was obtained. Further, through the soakingby pre-heating, the hardness of the welded portion after completion ofthe welding was able to be kept within a range of from 200 Hv to 500 Hv,thereby being capable of attaining high welding strength and stablewelding state and quality. Still further, the cup member 12 a and theshaft member 13 a were welded to each other under the condition that thepressure in the sealed space ill of the welding apparatus 100 was set toan atmospheric pressure or less, thereby being capable of suppressingthe change in pressure in the hollow cavity portion during the welding.As a result, the blowing of a molten material and the entry of themolten material toward the radially inner side were able to beprevented.

Following the above description of the overview of the manufacturingsteps (processing steps) of this embodiment, the features of thisembodiment, that is, the ultrasonic flaw detection-inspection step forthe welded portion is described with reference to FIG. 8 to FIG. 13.FIG. 8 is a front view for illustrating an overview of an ultrasonicflaw detection-inspection apparatus as viewed from the arrow G-G of FIG.9. FIG. 9 is a plan view for illustrating the ultrasonic flawdetection-inspection apparatus. In each of the states illustrated inFIG. 8 and FIG. 9, the outer joint member after welding is placed in theultrasonic flaw detection-inspection apparatus. FIG. 10 is a front viewfor illustrating a state during inspection as viewed from the arrow H-Hof FIG. 11. FIG. 11 is a plan view for illustrating the state duringinspection.

As illustrated in FIG. 8 and FIG. 9, an ultrasonic flawdetection-inspection apparatus 120 mainly comprises a water bath 122mounted at the center of a base 121, a workpiece support 123, aworkpiece holding member 124, a rotary drive device 125 configured torotate an intermediate product 11′ of the outer joint member 11(hereinafter also referred to as “workpiece 11′”), a pressing device 135configured to press an axial end of the workpiece 11′, and a drivepositioning device 136 (see FIG. 9) for a probe.

As illustrated in FIG. 8, the workpiece support 123 comprises rollers126 and 127 configured to allow the workpiece 11′ to be placed thereonin a freely rotatable manner. As illustrated in FIG. 9, the rollers 126and 127 are arranged in pairs so that the shaft section 13 of theworkpiece 11′ can be stably supported. The rollers 126 are located at aportion close to the welded portion, and the rollers 127 are located ata center portion of the shaft section 13. The rollers 126 and 127 arecapable of adjusting the placement position of the workpiece 11′ asappropriate in the axial direction (lateral direction of FIG. 9) and theradial direction (vertical direction of FIG. 9) in consideration of ajoint size, dimensions, and weight balance of the workpiece 11′.

Further, the workpiece holding member 124 is mounted to the workpiecesupport 123 at a position displaced from an axial line of the workpiece11′ in a horizontal direction (see FIG. 9). The workpiece holding member124 comprises a lever 128, and a workpiece holding roller 129 isarranged at an end portion of the lever 128. The lever 128 is pivotablein the plane, and is vertically movable.

The workpiece support 123 is mounted to a support 134 throughintermediation of a linear-motion bearing 130 comprising rails 131 andlinear guides 132, and is movable in the axial direction (lateraldirection of FIG. 8 and FIG. 9). The support 134 is mounted to the base121. A rod 1383 is coupled to an end portion (left end portion of FIG. 8and FIG. 9) of the workpiece support 123 so that the workpiece support123 is driven to be positioned by an actuator (not shown) on an outsideof the water bath 122.

The rotary drive device 125 comprises a rotary shaft 143 having a rotarydisc 144 mounted thereto, and this rotary shaft 143 is driven to rotateby a motor (not shown) on the outside of the water bath 122.

As illustrated in FIG. 8, a mounting base 137 is arranged on an upperside of the ultrasonic flaw detection-inspection apparatus 120. A baseplate 145 for the pressing device 135 configured to press the axial endof the workpiece 11′ is mounted to the mounting base 137 throughintermediation of a linear-motion bearing 138 comprising a rail 139 anda linear guide 140 so that the pressing device 135 is movable in theaxial direction (lateral direction of FIG. 8 and FIG. 9). A rod 142 of apneumatic cylinder 141 is coupled to an end portion of the base plate146 for the pressing device 135 so that the pressing device 135 isdriven. A free bearing 146 is mounted to a portion to be held inabutment against the axial end of the shaft section 13 of the workpiece11′ so that the axial end can be pressed in a freely rotatable manner.

As illustrated in FIG. 9, the drive positioning device 136 for a probeis arranged at a position displaced from the axial line of the workpiece11′ in a horizontal direction. This drive positioning device 136comprises actuators for the X-axis direction (lateral direction of FIG.9) and the Y-axis direction (vertical direction of FIG. 9) so that aprobe 147 is driven to be positioned in the X-axis and Y-axisdirections. An actuator 148 for the X-axis direction and an actuator 149for the Y-axis direction are each an electric ball-screw type (electriccylinder), which is capable of performing positioning with highaccuracy. Reference symbol 150 represents a rail for a linear-motionbearing. The drive positioning device 136 is arranged on the outside ofthe water bath 122, and the probe 147 and a holder 151 therefor arearranged in the water bath 122.

Next, the operation of the ultrasonic flaw detection-inspectionapparatus 120 and the ultrasonic flaw detection-inspection step S6 k aredescribed. As illustrated in FIG. 8 and FIG. 9, the workpiece 11′ afterwelding is placed on the workpiece support 123 by a loading device (notshown). At this time, in order that the workpiece 11′ is loaded, theworkpiece support 123 is located at an appropriate interval from therotary drive device 125 in the axial direction of the workpiece 11′, andthe workpiece holding member 124 raises and pivots the lever 128 thereofso as to be substantially parallel to the axial line of the workpiece11′. Further, the pressing device 135 and the drive positioning device136 for a probe wait at retreated positions.

After that, the lever 128 of the workpiece holding member 124 is pivotedso as to be substantially perpendicular to the axial line of theworkpiece 11′, and then lowered to hold the workpiece 11′ from above(see FIG. 10). Then, water is supplied to the water bath 122. In theultrasonic flaw detection-inspection apparatus 120 according to thisembodiment, flaw detection is performed under water, and henceultrasonic waves are satisfactorily propagated. Thus, inspection can beperformed with high accuracy.

Next, as illustrated in FIG. 10 and FIG. 11, the pneumatic cylinder 141is driven to cause the pressing device 135 to be advanced and pressedagainst the axial end of the workpiece 11′, thereby pressing the openingrim of the cup section 12 of the workpiece 11′ against the rotary disc144 of the rotary drive device 125. In conjunction with the advance ofthe pressing device 135, the workpiece support 123 is also moved towardthe rotary drive device 125. Thus, the workpiece 11′ is positioned inthe radial direction and the axial direction. In this state, the motor(not shown) of the rotary drive device 125 is rotated, thereby rotatingthe workpiece 11′.

As illustrated in FIG. 11, the drive positioning device 136 is moved inthe X-axis direction, and then moved in the Y-axis direction, therebypositioning the probe 147 at a flaw detection position (in FIG. 10, theprobe 147 in this state is indicated by the broken line). Then, theflaw-detection inspection is performed. After the flaw-detectioninspection, the water is drained, and the workpiece 11′ is unloaded fromthe ultrasonic flaw detection-inspection apparatus 120 by the loadingdevice (not shown). As described above, the inspection is sequentiallyrepeated on the workpieces 11′.

In the ultrasonic flaw detection-inspection apparatus 120 according tothis embodiment, in order to reduce the cycle time of the inspection,time-consuming supply and drainage of water are performed simultaneouslywith the operations of the devices and the members, or at other timingsin accordance therewith. Further, some of the operations of the devicesand the members may be performed simultaneously with each other or indifferent orders as appropriate.

Details of the ultrasonic flaw-detection inspection are described withreference to FIG. 12a , FIG. 12b , and FIG. 13. All of FIG. 12a , FIG.12b , and FIG. 13 are views as viewed from the arrow F-F of FIG. 10.FIG. 12a is an illustration of a non-defective welded product, and FIG.12b is an illustration of a defective welded product. FIG. 13 is anillustration of findings in the course of development.

The probe 147 is positioned at the flaw detection position away from thewelded portion 49 by a predetermined distance. The flaw detectionposition is preset for each joint size. A target welding depth isdenoted by the reference symbol Wa, and a minimum acceptable weldingdepth is denoted by the reference symbol Wmin. Workpieces having a depthequal to or larger than the minimum acceptable welding depth Wmin aredetermined as non-defective welded products, and workpieces having adepth smaller than the minimum acceptable welding depth Wmin aredetermined as defective welded products. When a transmission pulse G istransmitted at an incident angle θ1 from the probe 147, the transmissionpulse G is refracted by the surface of the shaft section 13, andadvances at a refraction angle θ2. The ultrasonic flaw-detectioninspection of this embodiment is performed under the condition that theincident angle θ1 is approximately 20°, and the refraction angle θ2 isapproximately 45°. During the flaw-detection inspection, the workpiece11′ is kept rotated by the rotary drive device 125 (see FIG. 10).

The probe 147 positioned at the flaw detection position away from thewelded portion 49 by the predetermined distance collects data of theentire periphery of the workpiece 11′. Specifically, in consideration oftolerance for displacement of the welding position, at theabove-mentioned flaw detection position, first, data of a singlerotation (360°) of the workpiece 11′ is collected. Then, the probe 147is sequentially shifted in the axial direction at a minute pitch (forexample, 0.5 mm) to collect data of a plurality of rotations (forexample, five rotations). Based on those pieces of data,non-defective/defective determination is made. A threshold of areflected echo to be used in the non-defective/defective determinationis determined based on a welding pattern corresponding to the minimumacceptable welding depth Wmin.

Advantages in the ultrasonic flow-detection inspection to be obtained bythe shape of the welded portion of the cup member 12 a and the shaftmember 13 a are described. As described above, the inner diameter D ofthe joining end surface 50 of the cup member 12 a is set smaller thanthe inner diameter E of the joining end surface 51 of the shaft member13 a. On the joining end surface 50 of the cup member 12 a, theprotruding surface 50 a protruding to the radially inner side withrespect to the inner diameter E of the joining end surface 51 of theshaft member 13 a is formed. In such a state, the cup member 12 a andthe shaft member 13 a are welded to each other.

Details of the advantages to be obtained by the shape of theabove-mentioned welded portion are described by way of an example ofcases of the non-defective welded product and the defective weldedproduct. In the case of the non-defective welded product, when thetransmission pulse G from the probe 147 is input as illustrated in FIG.12a , the transmission pulse G enters the cup section 12 through a backbead 49 a at the depth equal to or larger than the minimum acceptablewelding depth Wmin, and travels straight as it is. Alternatively, thetransmission pulse G is transmitted to the cup section 12 side by beingreflected due to the inner diameter D of the cup section 12. In thosecases, the probe 147 does not receive a reflected echo. This is because,as described above, on the joining end surface 50 of the cup member 12a, the protruding surface 50 a protruding to the radially inner sidewith respect to the inner diameter E of the joining end surface 51 ofthe shaft member 13 a is formed. Thus, even when the transmission pulseG enters the back bead 49 a, the boundary surface of the back bead 49 a,which is perpendicular to the transmission pulse G, does not exist. Forthis reason, although a slightly-scattered reflected echo is generated,the reflected echo does not have such an intensity as to cause adetection error of the probe 147. Thus, the intensity of the reflectedecho received by the probe 147 is equal to or less than the threshold,and hence determination that the welded product is non-defective ismade. As described above, when the protruding surface 50 a is formed onthe joining end surface 50 of the cup member 12 a, the intensity of thereflected echo is reduced. Thus, the accuracy in the inspection can beenhanced.

The findings in the course of the development to arrive at the shape ofthe welded portion of this embodiment are illustrated in FIG. 13. Inthis case, an inner diameter D′ of the joining end surface 50 of the cupmember 12 a is set to an equal dimension to the inner diameter E of thejoining end surface 51 of the shaft member 13 a. In this non-defectivewelded product, which has a welding depth equal to or larger than theminimum acceptable welding depth Wmin, when the transmission pulse Gfrom the probe 147 is input, due to the boundary surface of the backbead 49 a, which is perpendicular to the transmission pulse G, areflected echo R reflected by this boundary surface is received by theprobe 147. Although reflected echoes from the back bead 49 a arescattered, the reflected echo R is strong to have such an intensity asto be more than the threshold of the reflected echo for thenon-defective/defective determination. Thus, determination that thewelded product is defective is made. For this reason, it was proved thatthe determination as to whether the welded product was non-defective ordefective was difficult. Based on those findings, the inventors of thepresent invention arrived at the shape of the welded portion of thisembodiment.

Next, a case of a defective welded product is described. As illustratedin FIG. 12b , when the transmission pulse G from the probe 147 is inputunder a state in which a distal end of the back bead 49 a does not reachthe minimum acceptable welding depth Wmin, the transmission pulse G isreflected by the joining end surface 51 and a chamfered portion 61 a,and the scattered reflected echo R is received by the probe 147. Theintensity of the reflected echo R is more than the threshold of thereflected echo for the non-defective/defective determination, and hencedetermination that the welded product is defective is made. As describedabove, the protruding surface 50 a is formed on the joining end surface50, and hence the intensities of the reflected echoes can be clearlydiscriminated from each other. Thus, the determination as to whether thewelded product is non-defective or defective can be made with highaccuracy.

Dimensions of the protruding surface 50 a are set so that a relationshipof S≥Q is established, where S[S=(E−D)/2] is a width of the protrudingsurface 50 a in a radial direction, and where Q is a height of the backbead 49 a from the inner diameter E of the joining end surface 51 asillustrated in FIG. 12a . When this relationship is satisfied, theintensities of the reflected echoes can be clearly discriminated fromeach other. Thus, the determination as to whether the welded product isnon-defective or defective can be made with high accuracy. As long asthe relationship of S≥Q is maintained, the dimensions of the protrudingsurface 50 a may be changed as appropriate.

As described above, the ultrasonic flaw detection-inspection apparatus120 according to this embodiment mainly comprises the water bath 122mounted at the center of the base 121. In the water bath 122, theworkpiece support 123, the workpiece holding member 124, the rotary disc144 of the rotary drive device 126 configured to rotate the workpiece11′, the free bearing 146 of the pressing device 136 configured to pressthe axial end of the workpiece 11′, and the probe 147 mounted to thedrive positioning device 136 are arranged. With this configuration, theoperation of loading the workpiece 11′, the supply and drainage ofwater, the flaw-detection inspection, and the operation of unloading theworkpiece 11′ can be performed in conjunction with each other, and theultrasonic flaw-detection inspection can be automated. Thus, accuracy,operability, and efficiency in the inspection can be enhanced, which issuited to the inspection on the welded portion of the outer joint memberof the constant velocity universal joint being a mass-produced product.

Further, the outer diameter B of the joining end surface 60 of the cupmember 12 a of this embodiment is set to an equal dimension for eachjoint size. Also with this base configuration, in the ultrasonicflaw-detection inspection, setup operations with respect to the outerjoint members 11 having the different product numbers are simplified.Thus, the efficiency in the inspection can be further enhanced.

Still further, flaw detection is performed under water, and henceultrasonic waves are satisfactorily propagated. Thus, inspection can beperformed with much higher accuracy. In addition, through employment ofthe shape of the welded portion, in which the protruding surface 50 a isformed on the joining end surface 50, the intensities of the reflectedechoes can clearly be discriminated from each other. Thus, thedetermination as to whether the welded product is non-defective ordefective can be made with high accuracy.

To summarize the manufacturing concept, standardization of a producttype of the cup member is additionally described while exemplifying ashaft member having a product number different from that of theabove-mentioned shaft member 13 a of the long stem type illustrated inFIG. 5. A shaft member 13 b illustrated in FIG. 14 and FIG. 15 is usedas a general stem type on the inboard side. The shaft member 13 b hasthe joining end surface 51 to be brought into abutment against thejoining end surface 50 (see FIG. 4b ) of the bottom portion 12 a 2(projecting portion 12 a 3) of the cup member 12 a. The outer diameter Band the inner diameter E of the joining end surface 51 are set to theequal dimensions to the outer diameter B and the inner diameter E of thejoining end surface 51 of the shaft member 13 a of the long stem typeillustrated in FIG. 5. Also in this case, the inner diameter D of thejoining end surface 50 of the cup member 12 a is set smaller than theinner diameter E of the joining end surface 51 of the shaft member 13 b.On the joining end surface 50 of the cup member 12 a, the protrudingsurface 50 a protruding to the radially inner side with respect to theinner diameter E of the joining end surface 51 of the shaft member 13 bis formed. In such a state, the cup member 12 a and the shaft member 13b are welded to each other.

The shaft member 13 b is used as the general stem type on the inboardside. Accordingly, the shaft member 13 b comprises a shaft section witha small length, and a sliding bearing surface 18 formed on an axialcenter portion thereof, and a plurality of oil grooves 19 are formed inthe sliding bearing surface 18. The spline Sp and a snap ring groove 48are formed in an end portion of the shaft member 13 b on the sideopposite to the cup member 12 a side. As described above, even whenthere are differences in types, such as the general length stem type andthe long stem type, and shaft diameters and outer peripheral shapes varyin each vehicle type, the diameter B of the joining end surface 51 ofthe shaft member 13 a or 13 b is set to an equal dimension.

The outer diameter B of the joining end surface 50 of the cup member 12a and the joining end surface 51 of the shaft member 13 a or 13 b is setto an equal dimension for each joint size. Thus, the cup member preparedfor common use for each joint size, and the shaft member having avariety of specifications of the shaft section for each vehicle type canbe prepared in a state before heat treatment. Further, the intermediatecomponent of each of the cup member 12 a and the shaft member 13 a or 13b can be assigned with a product number for management. Whenstandardizing product types of the cup member 12 a, various types of theouter joint members 11 satisfying requirements can be produced quicklythrough combination of the cup member 12 a and the shaft member 13 a or13 b having a variety of specifications of the shaft section for eachvehicle type. Therefore, standardization of a product type of the cupmember 12 a can reduce cost and alleviate a burden of productionmanagement.

The standardization of the product type of the cup member is describedabove by taking the differences in types, such as the general lengthstem type and the long stem type, as an example for easy understanding,but the present invention is not limited thereto. The same applies tostandardization of the product type of the cup member for shaft membershaving a variety of specifications of the shaft section for each vehicletype among the general length stem types, and for shaft members having avariety of specifications of the shaft section for each vehicle typeamong the long stem types.

As a summary of the above description, FIG. 16 is a diagram forillustrating an example of standardization of a product type of the cupmember according to this embodiment. As illustrated in FIG. 16, the cupmember is prepared for common use for one joint size, and is assignedwith, for example, a product number C001 for management. In contrast,the shaft member has a variety of specifications of the shaft sectionfor each vehicle type, and is assigned with, for example, a productnumber S001, S002, or S(n) for management. For example, when the cupmember assigned with the product number C001 and the shaft memberassigned with the product number S001 are combined and welded to eachother, the outer joint member assigned with a product number A001 can beproduced. Thus, owing to standardization of a product type of the cupmember, it is possible to reduce cost and to alleviate a burden ofproduction management. In the standardization of a product type, the cupmember is not limited to one type for one joint size, that is, notlimited to one type assigned with a single product number. For example,the cup member comprises cup members of a plurality of types (assignedwith a plurality of product numbers, respectively) that are prepared forone joint size based on different specifications of a maximum operatingangle, and are each prepared so that the outer diameter B of the joiningend surface of each of those cup members has an equal dimension.

A modification of the outer joint member according to the firstembodiment is described with reference to FIG. 17 and FIG. 18. FIG. 17ais a partial vertical sectional view for illustrating an outer jointmember of this modification, FIG. 17b is an enlarged view forillustrating a circle “A” of FIG. 17a , and FIG. 17c is a view forillustrating a state before welding in FIG. 17b . FIG. 18 is a verticalsectional view for illustrating the entirety of a cup member beforewelding. A form of a protruding surface formed on a joining end surfaceof the cup member of this modification is different from that in thefirst embodiment, and other features are the same as those in the firstembodiment. Thus, parts that have the same function are denoted by thesame reference symbols (except for the subscripts), and only main pointsare described.

As illustrated in FIG. 17c and FIG. 18, a joining end surface 50 ₁formed on a projecting portion 12 ₁ a 3 of a bottom portion 12 ₁ a 2 ofa cup member 12 ₁ a is formed by annular turning. In this case, adiameter D₁ of the joining end surface 50 ₁ on the radially inner sidecorresponds to the inner diameter D of the joining end surface 50 of thecup member 12 a of the first embodiment. Thus, as illustrated in FIG.17c , a portion on the radially inner side with respect to the innerdiameter E of the shaft member 13 a corresponds to a protruding surface50 ₁ a. The cup member 12 ₁ a of this modification can be formed byturning an end surface of the projecting portion 12 a 3′ of the preform12 a′ for the above-mentioned cup member after ironing, which isillustrated in FIG. 4a , at only a portion corresponding to the joiningend surface 50 ₁ on the radially outer side as illustrated in FIG. 18.Thus, the time for the turning can be reduced. Note that, the presentinvention is not limited thereto, and a projecting surface portion 50 b₁ of the joining end surface on the radially inner side of FIG. 18 maybe subjected to turning.

Other features and advantages, that is, details of the overview of therespective steps, the states of the cup member and the shaft member inthe main processing steps, the preparation of the cup member for commonuse, the welding method, the ultrasonic flaw detection-inspectionmethod, the standardization of the product type, the configuration ofthe outer joint member, and the like as described above in the firstembodiment on the manufacturing method are the same as those of thefirst embodiment. Therefore, all the details of the first embodiment areapplied in this embodiment to omit redundant description.

FIG. 19 is an illustration of a manufacturing method according to asecond embodiment of the present invention. In the manufacturing stepsof this embodiment, the heat treatment step for the cup member, which isinvolved in the heat treatment step S7 in FIG. 3 as described above inthe first embodiment, is provided before the welding step S6 in thesequence and named “heat treatment step S5 c”, to thereby prepare thecup member as a finished product. Details of other aspects of the secondembodiment than this aspect, that is, details of the overview of therespective steps, the states of the cup member and the shaft member inthe main processing steps, the preparation of the cup member for commonuse, the welding method, the ultrasonic flaw detection-inspectionmethod, the standardization of the product type, the configuration ofthe outer joint member, and the like as described above in the firstembodiment on the manufacturing method are the same as those of thefirst embodiment. Therefore, all the details of the first embodiment areapplied in this embodiment, and only the difference is described.

As illustrated in FIG. 4b , the cup member 12 a has a shape extendingfrom the joining end surface 50 to the large-diameter cylindricalportion 12 a 1 via the bottom portion 12 a 2, and the portions to besubjected to heat treatment that involves quenching and tempering arethe track grooves 30 and the cylindrical inner peripheral surface 42located at the inner periphery of the cylindrical portion 12 a 1.Therefore, the cup member 12 a generally has no risk of thermal effecton the heat-treated portion during the welding. For this reason, the cupmember 12 a is subjected to heat treatment before the welding to beprepared as a finished component. The manufacturing steps of thisembodiment are suitable in practical use.

In the manufacturing steps of this embodiment, the cup member 12 a issubjected to heat treatment for preparing the cup member 12 a as afinished product, and is therefore assigned with a product numberindicating a finished product for management. Thus, the standardizationof the product type of the cup member 12 a remarkably reduces the costand alleviates the burden of production management. Further, the cupmember 12 a can be manufactured solely until the cup member 12 a iscompleted as a finished product through the forging, turning, and heattreatment. Thus, the productivity is enhanced by virtue of reduction ofsetups and the like as well.

In this embodiment, in FIG. 16 for illustrating the example ofstandardization of the product type of the cup member as described abovein the first embodiment, only the product number of the cup member inFIG. 16 is changed to the product number indicating a finished product,whereas the product numbers of the shaft member and the outer jointmember are the same as those of the first embodiment. Therefore,description thereof is omitted herein.

FIG. 20 is an illustration of a manufacturing method according to athird embodiment of the present invention. In the manufacturing steps ofthis embodiment, the heat treatment steps for the cup section and theshaft section, which are involved in the heat treatment step S7 in FIG.3 as described above in the first embodiment, and the grinding step S8for the shaft section in FIG. 3 are provided before the welding step S6in the sequence and named “heat treatment step S5 c for cup member”,“heat treatment step S4 s for shaft member”, and “grinding step S5 s”.Thus, both the cup member and the shaft member are prepared as finishedproducts. Details of other aspects of the third embodiment than thisaspect, that is, details of the overview of the respective steps, thestates of the cup member and the shaft member in the main processingsteps, the preparation of the cup member for common use, the weldingmethod, the ultrasonic flaw detection-inspection method, thestandardization of the product type, the configuration of the outerjoint member, and the like as described above in the first embodiment onthe manufacturing method are the same as those of the first embodiment.Therefore, all the details of the first embodiment are applied in thisembodiment, and only the difference is described.

After the spline processing step S3 s, a hardened layer having ahardness of approximately from 50 HRC to 62 HRC is formed in apredetermined range of the outer peripheral surface of the shaft memberby induction quenching in the heat treatment step S4 s. Heat treatmentis not performed on a predetermined portion in the axial direction,which includes the joining end surface 51. The heat treatment for thecup member, the assignment of the product number, and the like are thesame as those of the second embodiment on the manufacturing method, andredundant description is therefore omitted herein.

After the heat treatment step S4 s, the shaft member is transferred tothe grinding step S6 s so that the bearing mounting surface 14 and thelike are finished. Thus, the shaft member is obtained as a finishedproduct. Then, the shaft member is assigned with a product numberindicating a finished product for management. The manufacturing steps ofthis embodiment are suitable in a case of a cup member and a shaftmember having shapes and specifications with no risk of thermal effecton the heat-treated portion during the welding.

In the manufacturing steps of this embodiment, both the cup member andthe shaft member can be assigned with product numbers indicatingfinished products for management. Thus, the standardization of theproduct type of the cup member further remarkably reduces the cost andalleviates the burden of production management. Further, the cup memberand the shaft member can be manufactured independently of each otheruntil the cup member and the shaft member are completed as finishedproducts through the forging, turning, heat treatment, grinding afterheat treatment, and the like. Thus, the productivity is further enhancedby virtue of reduction of setups and the like as well.

In this embodiment, in FIG. 16 for illustrating the example ofstandardization of the product type of the cup member as described abovein the first embodiment, the product numbers of the cup member and theshaft member in FIG. 16 are changed to the product numbers indicatingfinished products. The product number of the outer joint member is thesame as that of the first embodiment. Therefore, description thereof isomitted herein. Note that, the cup member and the shaft member to beprepared as finished components are not limited to the cup member andthe shaft member subjected to finishing such as the above-mentionedgrinding after heat treatment or cutting after quenching, but encompassa cup member and a shaft member in a state in which the heat treatmentis completed while the finishing is uncompleted.

As described in the standardization of the product type, the cup memberis not limited to one type for one joint size, that is, not limited toone type assigned with a single product number. Specifically, asdescribed above, the cup member encompasses, for example, cup members ofa plurality of types (assigned with a plurality of product numbers,respectively) that are prepared for one joint size based on differentspecifications of a maximum operating angle, and are also prepared sothat the outer diameters B of the above-mentioned joining end surfacesof the cup members are set to equal dimensions. In addition, the cupmember encompasses, for example, cup members of a plurality of types(assigned with a plurality of product numbers, respectively) that areprepared for one joint size in order to achieve management of the cupmembers in a plurality of forms including intermediate components beforeheat treatment and finished components in consideration of the jointfunction, the circumstances at the manufacturing site, the productivity,and the like, and are also prepared so that the outer diameters B of theabove-mentioned joining end surfaces of the cup members are set to equaldimensions.

Next, an outer joint member according to a second embodiment of thepresent invention is described with reference to FIG. 21 and FIG. 22. Inthis embodiment, parts that have the same function as those of the outerjoint member according to the first embodiment are denoted by the samereference symbols, and only main points are described.

A plunging type constant velocity universal joint 102 illustrated inFIG. 21 is a tripod type constant velocity universal joint (TJ), andcomprises an outer joint member 11 ₂ comprising a cup section 12 ₂ andthe long stem section 13 that extends from a bottom portion of the cupsection 12 ₂ in the axial direction, an inner joint member 16 ₂ housedalong an inner periphery of the cup section 12 ₂ of the outer jointmember 11 ₂, and rollers 19 serving as torque transmitting elements thatare arranged between the outer joint member 11 ₂ and the inner jointmember 16 ₂. The inner joint member 16 ₂ comprises a tripod member 17comprising three equiangular leg shafts 18 on which the rollers 19 areexternally fitted.

Similarly to the outer joint member according to the first embodiment,the inner ring of the support bearing 6 is fixed to the outer peripheralsurface of the long stem section 13, and the outer ring of the supportbearing 6 is fixed to the transmission case with the bracket (notshown). The outer joint member 11 ₂ is supported by the support bearing6 in a freely rotatable manner, and thus the vibration of the outerjoint member 11 ₂ during driving or the like is prevented as much aspossible.

FIG. 22 is a partial vertical sectional view for illustrating the outerjoint member 11 ₂. As illustrated in FIG. 22, the outer joint member 11₂ comprises a bottomed cylindrical cup section 12 ₂ that is opened atone end and has inner peripheral surfaces 31 ₂ and the track grooves 30₂, on which the rollers 19 (see FIG. 21) are caused to roll, formed atthree equiangular positions on an inner peripheral surface of the cupsection 12 ₂, and the long stem section 13 that extends from a bottomportion of the cup section 12 ₂ in the axial direction and comprises thespline Sp serving as the torque transmitting coupling portion formed atthe outer periphery of the end portion on the opposite side to the cupsection 12 ₂ side. The outer joint member 11 ₂ is formed by welding thecup member 12 ₂ a and the shaft member 13 a to each other.

As illustrated in FIG. 22, the cup member 12 ₂ a is an integrally-formedproduct having a cylindrical portion 12 ₂ a 1 and a bottom portion 12 ₂a 2. The cylindrical portion 12 ₂ a 1 has the track grooves 30 ₂ and theinner peripheral surfaces 31 ₂ formed at the inner periphery thereof. Aprojecting portion 12 ₂ a 3 is formed at the bottom portion 12 ₂ a 2 ofthe cup member 12 ₂ a. The boot mounting groove 32 is formed at an outerperiphery of the cup member 12 ₂ a on the opening side thereof. Thebearing mounting surface 14 and the snap ring groove 15 are formed atthe outer periphery of the shaft member 13 a on the cup member 12 ₂ aside, whereas the spline Sp is formed at the end portion on the oppositeside to the cup member 12 ₂ a side.

A joining end surface 50 ₂ formed at the projecting portion 12 ₂ a 3 ofthe bottom portion 12 ₂ a 2 of the cup member 12 ₂ a and the joining endsurface 51 formed at the end portion of the shaft member 13 a on the cupmember 12 ₂ a side are brought into abutment against each other, and arewelded to each other by electron beam welding performed from theradially outer side. The welded portion 49 is formed of a bead, which isformed by a beam radiated from the radially outer side of the cup member12 ₂ a. Similarly to the outer joint member of the first embodiment, theouter diameters B of the joining end surface 50 ₂ and the joining endsurface 51 are set to equal dimensions for each joint size. The weldedportion 49 is formed on the joining end surface 51 located on the cupmember 12 ₂ a side with respect to the bearing mounting surface 14 ofthe shaft member 13 a, and hence the bearing mounting surface 14 and thelike can be processed in advance so that post-processing after weldingcan be omitted. Further, due to the electron beam welding, burrs are notgenerated at the welded portion. Thus, post-processing for the weldedportion can also be omitted, which can reduce the manufacturing cost.

The details of the outer joint member according to this embodiment arethe same as the details of the outer joint member according to the firstembodiment, and the manufacturing method according to the first to thirdembodiments as described above. Therefore, all of those details areapplied in this embodiment to omit redundant description.

In the above-mentioned embodiments and the above-mentionedmodifications, the case where the protruding surface is formed on theradially inner side with respect to the joining end surface of the cupmember is exemplified. However, conversely, the protruding surface maybe formed on the radially inner side with respect to the joining endsurface of the shaft member. In this case, there are no problems as longas the ultrasonic flaw-detection inspection is performed from a surfaceside of the cup member.

In the above-mentioned embodiments and the above-mentionedmodifications, the case to which electron beam welding is applied isdescribed, but laser welding is also similarly applicable.

In the outer joint member according to the embodiments and themodifications described above, the cases where the present invention isapplied to the double-offset type constant velocity universal joint asthe plunging type constant velocity universal joint 10, and to thetripod type constant velocity universal joint as the plunging typeconstant velocity universal joint 10 are described. However, the presentinvention may be applied to an outer joint member of another plungingtype constant velocity universal joint such as a cross-groove typeconstant velocity universal joint, and to an outer joint member of afixed type constant velocity universal joint. Further, in the above, thepresent invention is applied to the outer joint member of the constantvelocity universal joint, which is used to construct the drive shaft.However, the present invention may be applied to an outer joint memberof a constant velocity universal joint, which is used to construct apropeller shaft.

The present invention is not limited to the above-mentioned embodimentsand the above-mentioned modifications. As a matter of course, variousmodifications can be made thereto without departing from the gist of thepresent invention. The scope of the present invention is defined inClaims, and encompasses equivalents described in Claims and all changeswithin the scope of claims.

DESCRIPTION OF REFERENCE SIGNS

-   -   1 drive shaft    -   2 intermediate shaft    -   3 spline    -   4 boot    -   5 boot    -   6 support bearing    -   10 plunging type constant velocity universal joint    -   11 outer joint member    -   12 cup section    -   12 a cup member    -   12 a 1 cylindrical portion    -   12 a 2 bottom portion    -   13 long shaft section    -   13 a shaft member    -   14 bearing mounting surface    -   16 inner joint member    -   17 tripod member    -   19 torque transmitting element (roller)    -   20 fixed type constant velocity universal joint    -   21 outer joint member    -   22 inner joint member    -   23 torque transmitting element (ball)    -   24 cage    -   30 track groove    -   31 inner peripheral surface    -   40 track groove    -   41 torque transmitting element (ball)    -   42 cylindrical inner peripheral surface    -   49 welded portion    -   50 joining end surface    -   50 a protruding surface    -   51 joining end surface    -   52 recessed portion    -   100 welding apparatus    -   101 electron gun    -   108 case    -   109 vacuum pump    -   111 sealed space    -   120 ultrasonic flaw detection-inspection apparatus    -   121 base    -   122 water bath    -   123 workpiece support    -   124 workpiece holding member    -   125 rotary drive device    -   135 pressing device    -   136 drive positioning device for probe    -   147 probe    -   B outer diameter    -   D inner diameter    -   E inner diameter    -   G transmission pulse    -   R reflected echo    -   O joint center    -   O1 curvature center    -   O2 curvature center    -   Sp spline

The invention claimed is:
 1. A method of manufacturing an outer jointmember of a constant velocity universal joint, which is constructed byforming, through use of separate members, a cup section having trackgrooves formed at an inner periphery of the cup section and engageablewith torque transmitting elements, and a shaft section formed at abottom portion of the cup section, and by welding a cup member formingthe cup section and a shaft member forming the shaft section, the methodcomprising: forming the cup member and the shaft member of medium carbonsteel; preparing, as the cup member, a cup member having a cylindricalportion and a bottom portion integrally formed by forging, and a joiningend surface formed on an outer surface of the bottom portion in amachining step after the forging; preparing, as the shaft member, ashaft member having a joining end surface to be joined to the bottomportion of the cup member, which is formed in a machining step; bringingthe joining end surface of the cup member and the joining end surface ofthe shaft member into abutment against each other; welding the cupmember and the shaft member by radiating a beam from an outer side ofthe cup member to an abutment portion between the cup member and theshaft member in a radial direction of the cup member, the joining endsurface of the cup member having an outer diameter set to an equaldimension for each joint size, the welding being performed under a statein which a protruding surface protruding to a radially inner side withrespect to an inner diameter of another one of the joining end surfaceof the cup member and the joining end surface of the shaft member isformed on a radially inner side of any one of the joining end surface ofthe cup member and the joining end surface of the shaft member; andperforming, after the welding, ultrasonic flaw detection-inspection fromany one of a surface side of the cup member and a surface side of theshaft member, which has the another one of the joining end surface ofthe cup member and the joining end surface of the shaft member.
 2. Themethod of manufacturing an outer joint member of a constant velocityuniversal joint according to claim 1, wherein the ultrasonic flawdetection-inspection comprises performing flaw detection under a statein which the cup member and the shaft member after the welding areplaced under water.
 3. The method of manufacturing an outer joint memberof a constant velocity universal joint according to claim 2, wherein theprotruding surface is formed into the same shape for each joint size. 4.The method of manufacturing an outer joint member of a constant velocityuniversal joint according to claim 1, wherein the protruding surface isformed into the same shape for each joint size.
 5. The method ofmanufacturing an outer joint member of a constant velocity universaljoint according to claim 1, wherein the protruding surface is formed onthe joining end surface of the cup member, and wherein the ultrasonicflaw detection-inspection comprises inputting an ultrasonic wave with anangle probe from the surface side of the shaft member.
 6. The method ofmanufacturing an outer joint member of a constant velocity universaljoint according to claim 1, wherein at least one of the cup member orthe shaft member before the welding is prepared as an intermediatecomponent without performing heat treatment.
 7. The method ofmanufacturing an outer joint member of a constant velocity universaljoint according to claim 1, wherein at least one of the cup member orthe shaft member before the welding is prepared as a finished componentsubjected to heat treatment.
 8. The method of manufacturing an outerjoint member of a constant velocity universal joint according to claim1, wherein the welding comprises electron beam welding.
 9. The method ofmanufacturing an outer joint member of a constant velocity universaljoint according to claim 1, wherein the welding comprises welding thecup member and the shaft member under a state in which the cup memberand the shaft member are placed in a sealed space to keep a pressureequal to or less than an atmospheric pressure.